As one method of manufacturing a semiconductor device, a process of supplying a cleaning gas into a processing chamber and cleaning the inside of the processing chamber is performed after a process of forming a thin film on a substrate is performed in the inside of the processing chamber. In the related art, there is known a cleaning method including an etching process of unilaterally supplying a fluorine gas or a fluorine gas diluted with an inert gas as a cleaning gas into a processing chamber heated to a first temperature and removing a thin film deposited inside of the processing chamber, and a treatment process of removing extraneous materials remaining in the inside of the processing chamber after the thin film is removed.
However, in the etching process of unilaterally supplying the fluorine gas or the fluorine gas diluted with the inert gas as the cleaning gas into the processing chamber and removing the thin film deposited in the inside of the processing chamber, particularly in a low-temperature condition of less than 400, the time required to remove the thin film is lengthened. Depending on conditions, the etching selection ratio of the thin film to quartz (SiO2) may be lowered, and a quartz member constituting the processing chamber may receive an uneven etching damage.